Intraocular lens systems and methods

ABSTRACT

An intraocular lens ( 31 ) which may be used as a posterior lens in a lens train including a converging anterior lens ( 20 ) and diverging posterior lens ( 31 ) in which the optical/focal axes of the two lenses are not coincident such that the focal point ( 9 ) of the lens train is offset from the focal axis of the anterior lens. Light rays ( 50 ) incident upon the anterior lens parallel to its focal axis may thus be directed ( 51 ) to parts of the retina offset from the fovea where the macula may not have degenerated.

The present invention relates to intraocular lenses, methods of theiruse and methods of their manufacture.

FIG. 1 illustrates schematically a cross-section view of a natural eye(1) such as a human eye. The eye includes a cornea (2), an iris (3), alens (4) defining a central optical axis (5), a ciliary sulcus (6)connected to the lens by a zonal ligament (7), a retina (8) with amacula (9) at its central region centred upon a fovea (10) where thecentral axis (5) of the lens intersects the retina. An anterior sac (11)is bounded by the cornea and the iris. A posterior sac (12) is boundedby the iris and the retina, and contains the lens.

Light rays (not shown) parallel to the central axis of the lens andincident upon the cornea are able to be focussed by the refractive poserof the cornea and lens incident upon the macula at the fovea of the eye.Light rays striking the cornea obliquely are unfocussed and provide lessacute, peripheral vision.

Degeneration or damage of the retina at the macula (known as maculadegeneration) reduces the ability of the retina to detect light incidentthere. This greatly reduces visual acuity by degenerating those regionsof the retina upon which the eye is arranged to form focussed images.Such degeneration typically results in a blurred spot or dark spotforming at the centre of vision where, prior to degeneration, a focussedimage would be. Peripheral vision remains largely unaffected.

The invention aims to provide means and methods which may be useful inaddressing the problem of overcoming the loss of visual acuity throughmacular degeneration.

In ophthalmology, the term “haptic” is used to refer to a supportinglimb, arm or spring which is used to hold an artificial lens within aneye (e.g. after surgical removal of cataracts or of the natural lens forother reasons).

At its most general, the invention proposed is means and methodsinvolving an intraocular lens which may be used as a posterior lens in alens train (e.g. intraocular) including a converging anterior lens anddiverging posterior lens in which the optical/focal axes of the twolenses are not coincident (but are preferably parallel) such that thefocal point of the lens train is offset from the focal axis of theanterior lens. Light rays incident upon the anterior lens parallel toits focal axis may thus be directed to parts of the retina offset fromthe fovea where the macula may not have degenerated.

In a first of its aspects, the invention may provide an intraocular lensapparatus, most preferably a posterior intraocular lens apparatus,including: diverging lens means shaped to define as between oppositeoperative lens surfaces a lens part of minimal lens thickness surroundedby lens parts of greater lens thickness; haptic means extending from thediverging lens means to a first haptic part at an intermediate distancefrom the lens part of minimal lens thickness, and further extending fromthe diverging lens means (e.g. further extending from the first hapticpart) to a second haptic part at a maximal distance from the lens partof minimal lens thickness; wherein the maximal distance is greater thanthe intermediate distance and the second haptic part opposes the firsthaptic part across the lens part of minimal lens thickness. Thus, theapparatus may have a haptic containing both the first and second hapticparts. The plane containing the two haptic parts may thus contain orincorporate the lens part of minimal lens thickness, or a part of it(e.g. focal axis at the optical centre of the lens). The haptic meansmay be the sole haptic attached to the diverging lens means.

The haptic means may comprise an arcuate limb incorporating the firstand second haptic parts. The arcuate limb may be an arcuate spiral whichspirals progressively outwardly of the diverging lens from the firsthaptic part to the second haptic part. The limb may be at least partlysemicircular. The first and second haptic parts may reside atdiametrically opposed parts of a semicircular haptic arc connected tothe diverging lens means. The haptic means may arc around the diverginglens to such an extent as to subtend about the lens part of minimal lensthickness, an angle equal to or greater than 180 degrees. In this way, asingle haptic may be provided which is substantially coplanar with theplane of the diverging lens from which it extends rendering it mostsuitable for use as an intraocular lens in the posterior sac of the eye.

In a second of its aspects, the invention may provide an intraocularlens apparatus, most preferably a posterior intraocular lens apparatus,including: diverging lens means shaped to define as between oppositeoperative lens surfaces a lens part of minimal lens thickness surroundedby lens parts of greater lens thickness; a first haptic means extendingfrom the diverging lens means to a first haptic part at a first maximaldistance from the lens part of minimal lens thickness; a second hapticmeans separate from the first haptic means and extending from thediverging lens means to a second haptic part at a second maximaldistance from the lens part of minimal lens thickness; wherein thesecond maximal distance is greater than the first maximal distance.Accordingly, two separate haptics may be employed and either the hapticsand/or the structure of the diverging lens, may be adapted and arrangedto provide the difference in the maximal distances associated withrespective haptics.

According to any aspect of the invention, the lens part of minimalthickness may define a central axis perpendicular to, and passingthrough, opposing and instantaneously parallel operative lens surfaces.The lens part of minimal lens thickness may coincide with the opticalaxis of the lens which also contains the focal points of the lens. Inthis way, the diverging lens apparatus may be used in combination withanother lens, such as a converging lens, to provide a lens train havinga magnifying power. Not only may the diverging lens divert incominglight to a suitable part of the macula, but may also cooperate with ananterior lens (e.g. converging lens) to magnify the image formed by thelens train at the macula. Magnifications of up to about 1.5 are suitablyprovided (e.g. 1.2 to 1.4).

The first haptic part may oppose the second haptic part across the lenspart of minimal lens thickness. The plane containing the two opposinghaptic parts may also contain or incorporate the lens part of minimallens thickness, or a part of it.

One or each of the first and second haptic means respectively maycomprise an arcuate limb. The arcuate limb of a given haptic may be ahook shape or part spiral shape. It may extend initially away from, butsubsequently towards, a periphery of the diverging lens, passing througha turning point in the limb. The first (or second) haptic part may residat the turning point. Those parts of the haptics where the first/secondhaptic part reside may extent in a direction transverse to the linebetween the first and second haptic parts. In this way, the first/secondhaptic parts may present the outermost extent of the apparatus as atangential haptic surface suitable for sliding movement against an innerwall of an eye without “snagging”.

The lens part of minimal thickness may define between nearmost opposingoperative lens surface, an axis perpendicular to, and passing through,both represents the optical axis of the lens containing the focalpoint(s) of the lens.

The lens part of minimal lens thickness may be substantially in themiddle or centroid of the operative lens surface(s). For example, thediverging lens may have a substantially circular outermost peripherycentred upon the lens part of minimal lens thickness. An, or each,operative lens surface may be generally symmetrical in shape and extentabout the optical axis of the lens (e.g. in any radial directiontherefrom).

The lens part of minimal lens thickness may be offset from the middle orcentroid of the operative lens surface(s) towards a periphery thereof.For example, the diverging lens may have a substantially circularoutermost periphery which is not centred upon the lens part of minimallens thickness.

A plane containing first and second haptic parts may contain, include orintersect the lens part of minimal lens thickness.

The periphery of the diverging lens means may present a sighting means,or recognition point, indicating the peripheral part of the diverginglens means located between (e.g. in-line between) the second haptic partand the lens part of minimal lens thickness. The lens apparatus isemployed as a posterior lens in a posterior aperture of the eye (ciliarysulcus), This positioning of the sighting means indicates the directionin which light will be refracted by the posterior lens when used incombination with a converging anterior lens as described below.

The first and second haptic parts may be peripheral parts (e.g. mostperipheral) of the apparatus. The lens apparatus, when positioned in ananterior eye aperture, may be turned about the central axis of theaperture so as to revolve the lens part of minimal lens thickness, andthe recognition point if used, about the central axis to enable the userto select a desired direction of light diversion to a desired region ofthe macular.

The diverging lens means may comprise a plano-concave lens, or maycomprise a concavo-concave lens (e.g. bi-concave).

The diverging lens means may be flexible, preferably to an extentsufficient to permit the lens to be rolled-up and unrolled. It may bemade of hard hydrophilic acrylic material such as polymethylmethacrylate(PMMA) etc, or soft hydrophilic or hydrophobic acrylicmaterial including but not limited to polymers containing hydroxyethylmethacrylate (HEMA), silicon hydrogel, etc.

The diverging lens means may be adapted for use as a posteriorintraocular lens and the apparatus may further comprise a converginglens means adapted to cooperate with the diverging lens means as ananterior intraocular lens.

The apparatus may be sold in kit form or as a kit of parts (e.g. withinstructions for use) and the invention may provide a kit of partscomprising the converging and diverging lens means as described herein.

The converging lens means may include one or more haptics which extendaway from the converging lens means in a direction partially transverseto the plane containing the circumference of the lens to one common sideof that plane.

The converging lens means may be shaped to define as between oppositeoperative lens surfaces a lens part of maximal lens thickness surroundedby lens parts of lesser lens thickness and includes a third haptic meansextending from the converging lens means to a third haptic part at athird maximal distance from the lens part of maximal lens thickness, anda fourth haptic means separate from the third haptic means and extendingfrom the converging lens means to a fourth haptic part at a fourthmaximal distance from the lens part of maximal lens thickness.

In a third of its aspects, the invention may provide a method ofproviding a lens train for forming an image of an object or sceneincluding: providing an intraocular lens apparatus as described above;placing the converging lens means between the diverging lens means andthe object or scene to be imaged such that an operative lens surface ofthe converging lens means opposes an operative lens surface of thediverging lens means and such that the lens part of minimal lensthickness does not oppose the lens part of maximal thickness.

The method may include providing a first (e.g. substantially circular)aperture (e.g. ciliary sulcus) in parallel opposition to a second (e.g.substantially circular) aperture (e.g. anterior sac wall circumscribingthe iris) such that the centres of the first and second apertures are inregister; mounting the diverging lens means within the first aperturesuch that haptics thereof abut opposite first aperture edges; mountingthe converging lens means within the second aperture such that hapticsthereof abut opposite second aperture edges.

The method may include rotating the mounted diverging lens means withinthe first aperture thereby to revolve the lens part of minimal lensthickness about the centre of the first aperture thereby to select thelocation of images formable by the lens train in use.

In a fourth of its aspects, the invention may provide a method ofmanufacturing an intraocular lens (preferably a posterior intraocularlens) such as is described above including: providing a lens template;shaping (e.g. lathing) inner surface parts of the lens template todefine opposite surfaces of a lens (e.g. concave or bi-concave) betweenwhich is defined a lens part of minimal lens thickness surrounded bylens parts of greater lens thickness; shaping (e.g. milling or cutting)outer surface parts of the lens template around said inner surface partsto form said diverging lens means and said haptic(s). The operative lenssurfaces may be polished after being shaped.

The method may include shaping portions of said inner surface partsdefining said lens to form said diverging lens means and said haptic(s).

The method may include shaping said inner surface parts to form asymmetrical concavity with a circular periphery centred upon the lenspart of minimal lens thickness and forming therefrom the diverging lensmeans with a lens periphery centred upon other than the lens part ofminimal lens thickness.

The lens train described above may posses an axial offset (Δ) resultingfrom an axial offsetting of the focal axis of the posterior and anteriorlenses by between about 0.5 m and 2.0 mm. The angular deviation of thefocal point of the lens train relative to the furthest focal point ofthe diverging (posterior) lens may be up to about 15 degrees. Theanterior converging lens may have a positive power of between about 50and 60 dioptres (e.g. +53 dioptres). The posterior lens may be locatedwithin the focal length of the anterior lens, and the anterior lens maybe located within the focal length of the posterior lens. The anteriorlens (excluding haptic lengths) may be between about 4 mm and 7 mm (e.g.5 mm) in diameter. Haptics may extend to a maximal distance fromopposite edges of the anterior lens of between 3 mm and 6 mm (e.g. 4 mm)therefrom each. The diverging lens may have a negative optical power ofbetween about −55 and −70 dioptres (e.g. −64 dioptres). The diverginglens may be between 5 mm and 9 mm (e.g. 7 mm) in diameter and may have alesser haptic (containing the first haptic part) extending from the edgeof the diverging lens to a maximal distance of between about 1.5 and 3mm (e.g. 2 mm) therefrom. The diverging lens may have a greater haptic(containing the second haptic part) extending from the (e.g. oppositeedge of the) posterior lens to a maximal distance of between about 3 mmand 6 mm (e.g. 4 mm) thereform. The diverging lens unit may be betweenabout 10 m and 16 mm (e.g. 13 mm) across at its widest point.

There now follows a description of some illustrative, but non-limitingand non-exhaustive, examples of embodiments of the invention withreference to the drawings of which:

FIG. 1 illustrates a cross-sectional view of the natural (e.g. Human)eye;

FIGS. 2A and 2B illustrate a plan view (FIG. 2A) and a side view (FIG.2B) of an anterior intraocular lens apparatus with symmetrical haptics;

FIGS. 3A and 3B illustrate a plan view (FIG. 3A) and a side view (FIG.3B) of a posterior intraocular lens apparatus with asymmetrical haptics;

FIGS. 4A and 4B illustrate a plan view (FIG. 4A) and a side view (FIG.4B) of a posterior intraocular lens apparatus symmetrical haptics;

FIG. 5 illustrates a cross-sectional view of the natural (e.g. Human)eye including an anterior intraocular lens apparatus of FIGS. 2A and 2Bin the anterior sac and a posterior intraocular lens apparatus of FIGS.3A and 3B in the posterior sac in place of the natural lens;

FIG. 6 illustrates a cross-sectional view of the natural (e.g. Human)eye including an anterior intraocular lens apparatus of FIGS. 2A and 2Bin the anterior sac and a posterior intraocular lens apparatus of FIGS.4A and 4B in the posterior sac in place of the natural lens;

FIG. 7 schematically illustrates an optical train comprising an anteriorconverging lens and a posterior lens with central axes relativelyoffset;

FIG. 8 schematically illustrates an optical train comprising an anteriorlens and a posterior diverging lens with central axes relatively offsetand the resulting axial offsetting of images formed thereby;

FIGS. 9 and 10 schematically illustrate examples of an optical traincomprising an anterior converging lens apparatus and a posteriordiverging lens apparatus with central axes relatively offset by virtueof asymmetric haptics or asymmetric posterior lens structures;

In the drawings, like items are assigned like reference symbols.

FIGS. 2A and 2B illustrate views of an anterior intraocular lens unit(20) including a converging lens (21) shaped to define as betweenopposite operative anterior lens surfaces a lens part of maximalthickness (22) surrounded by lens parts of lesser lens thickness (23).The lens part of maximal thickness defines a central axis perpendicularto, and passing through, opposing and instantaneously parallel operativeanterior lens surfaces (28, 29). This axis coincides with the opticalaxis of the converging lens which also contains the focal points of thelens.

The anterior lens unit has a first serpentine anterior haptic limb (24)extending away from the converging lens to a first anterior haptic part(25) at a first anterior maximal distance from the lens part of maximallens thickness. A second serpentine anterior haptic limb (26) separatefrom the first anterior haptic limb, extends from a part of theconverging lens diametrically opposed to that part from which the firstserpentine anterior haptic limb extends, and so extends to a secondanterior haptic part (27) at a second anterior maximal distance from thelens part of maximal lens thickness. The first and second anteriormaximal distances are substantially equal. At their maximal distances,the first and second anterior haptic parts are defined by respectivehaptic limb parts which are generally oriented in a direction tangentialto a bounding circle geometrically bounding the anterior lens unit andcentred upon the central axis of the converging lens. Accordingly, theoutermost parts of the anterior lens unit are equidistant from thecentral axis and opposed across it. They present osculating and locallyparallel abutting surfaces to the inner circular edge of a circularaperture corresponding to the bounding circle (e.g. an aperture in theeye). The serpentine nature of the haptic limbs provides a resilience orspringiness via which the anterior lens unit may hold the converginglens centrally in registered with such an aperture.

Each of the anterior haptics extends away from the converging lens in adirection oblique to (i.e. partly parallel to, and partially transverseto) the plane (200) containing the circumference of the lens to onecommon side of that plane. As a result, the anterior lens is adapted tobe placed within the anterior sac of the eye (4) over, and centrally inregister with, the aperture of the iris (3).

FIGS. 3A and 3B show views of a posterior intraocular lens unit (30)including a diverging lens (31) shaped to define as between oppositeoperative lens surfaces a lens part of minimal lens thickness (32)surrounded by lens parts of greater lens thickness (33). The posteriorlens unit has a first arcuate posterior haptic (34) extending from thediverging lens to a first posterior haptic part (35) at a firstposterior maximal distance (d1) from the lens part of minimal lensthickness. A second arcuate posterior haptic (36), separate from thefirst posterior haptic, extends away from a part of the diverging lensdiametrically opposed to that part from which the first arcuateposterior haptic extends, and so extends to a second posterior hapticpart (37) at a second posterior maximal distance (d2) from the lens partof minimal lens thickness.

The second posterior maximal distance is greater than the firstposterior maximal distance (i.e. d2>d1). At their maximal distances, thefirst and second posterior haptic parts are defined by respectivearcuate haptic limb parts which are generally oriented in a directiontangential to a bounding circle geometrically bounding the posteriorlens unit and offset from the central axis of the diverging lens.Accordingly, the outermost parts of the posterior lens unit are opposedacross the centre of the bounding circle the central axis. However,while those parts are equidistant from the centre of the boundingcircle, they are not equidistant from the central axis of the diverginglens such that the central axis is offset from the centre of thebounding circle. They present osculating and locally parallel abuttingsurfaces to the inner circular edge of a circular aperture correspondingto the bounding circle (e.g. an aperture in the eye). The arcuate natureof the haptic limbs provides a resilience or springiness via which theposterior lens unit may hold the diverging lens within such an aperturewith the central axis of the lens axially offset from the centre of theaperture.

FIG. 3B shows the lens unit of FIG. 3A in side view schematically andshowing the diverging lens in cross-sectional view to illustratecurvature, while the haptics are shown in full side view to illustratethe radial extent to which they extend or project from the lens part ofminimal thickness (32).

The lens part of minimal thickness defines a central axis perpendicularto, and passing through, opposing and instantaneously parallel operativelens surfaces (38, 39). This axis coincides with the optical axis of thelens which also contains the focal points of the lens.

Each of the posterior haptics extends away from the diverging lens in adirection parallel to, and within, the plane (300) containing thecircumference of the lens. As a result, the anterior lens is adapted tobe placed within the posterior sac of the eye (12) behind the apertureof the iris and in place of the natural lens (4) of the eye.

FIGS. 4A and 4B show views of another embodiment of a posteriorintraocular lens unit (40) including a diverging lens (41) shaped todefine as between opposite operative lens surfaces a lens part ofminimal lens thickness (42) surrounded by lens parts of greater lensthickness (43). The posterior lens unit has a first arcuate posteriorhaptic (44) extending from the diverging lens to a first posteriorhaptic part (45) at a first posterior maximal distance (d2) from thelens part of minimal lens thickness. A second arcuate posterior haptic(46), separate from the first posterior haptic, extends away from a partof the diverging lens diametrically opposed to that part from which thefirst arcuate posterior haptic extends. It so extends to a secondposterior haptic part (47) at a second posterior maximal distance (d1)from the lens part of minimal lens thickness. The second posteriormaximal distance is less than the first posterior maximal distance (i.e.d2>d1).

The first and second posterior haptics (44,45) are substantially ofequal length. At their maximal distances, which do not coincide withtheir ends, the first and second posterior haptic parts are defined byrespective arcuate haptic limb parts which are generally oriented in adirection tangential to a bounding circle (locus) geometrically definingthe extreme limits of the posterior lens unit and notionally boundingit. The geometrical centre of the bounding circle does not coincide withthe central axis (42) of the diverging lens. As a result, the outermostparts of the posterior lens unit (45, 47) are opposed to each otheracross the centre of the bounding circle the central axis of the lens.Those parts are equidistant from the centre of the bounding circle. Theyare not also equidistant from the central axis (42) of the diverginglens. The central axis is thereby offset from the centre of the boundingcircle. The extreme haptic parts of the lens unit present abuttingsurfaces which are arranged to be locally parallel to the inner circularedge of a circular aperture corresponding to the bounding circle (e.g.an aperture in the eye). The arcuate spiral nature of the haptic limbsprovides a resilience or springiness via which the posterior lens unitmay hold the diverging lens within such an aperture with the centralaxis of the lens axially offset from the centre of the aperture.

FIG. 4B shows the lens unit of FIG. 4A in side view schematically andshowing the diverging lens in cross-sectional view to illustratecurvature, while the haptics are shown in full side view to illustratethe radial extent to which they extend or project from the lens part ofminimal thickness (42). The condition d2>d1 applicable to this lens(both FIGS. 4A and 4B) can be seen explicitly.

The lens part of minimal thickness defines a central axis perpendicularto, and passing through, opposing and instantaneously parallel operativelens surfaces (48, 49). This axis coincides with the optical axis of thelens which also contains the focal points of the lens.

Each of the posterior haptics extends away from the diverging lens in adirection parallel to, and within, the plane (400) containing thecircumference of the lens. As a result, the anterior lens is adapted tobe placed within the posterior sac of the eye (12) behind the apertureof the iris and in place of the natural lens (4) of the eye.

The first and second arcuate posterior haptics of FIGS. 3A, 3B, 4A and4B are shaped as spiral arms which extend from and around the lens aboutits central axis in a common angular sense subtending about 90 degreesfrom end to end at the lens centre. Between the outermost haptic partand the terminal end of each haptic limb, the limb approaches the lens.Furthermore, peripheral outermost edge of the converging lens, in eachcase, presents a sighting lug (350, 450) in-line with the linecontaining the outermost posterior haptic parts and the central axis ofthe lens. The sighting lug, or recognition point, indicates thedirection, relative to the central axis, in which light emanating fromthe anterior lens will be directed when the posterior and anterior lensunits are co-arranged in the manner illustrated in FIGS. 5 and 6.Furthermore, in embodiments of the invention such as shown in FIGS. 3Aand 3B and 5, haptics extend by differing amounts from the local lensperiphery. By locating the sighting lug at the lens periphery facing thelonger of the two haptics (36), the user is better able to see thesighting lug via the aperture of the iris when the posterior lens unitis being positioned there. For example, the haptic dimension may bechosen such that the sighting lug is adjacent, or just below, an edge ofthe iris when the eye is viewed externally.

FIG. 5 schematically illustrates a cross-section view of an eye (1) inwhich an anterior lens unit (20) of the type illustrated in FIGS. 2A and2B is inserted into the anterior sac (11) of the eye centrally inregister with the centre of the aperture of the iris (3). The serpentineanterior haptics (24, 26) abut the circular wall parts of the eyeimmediately adjacent parts thereof to which the iris is attached. Thisabutment holds the anterior lens in place. A posterior lens unit (30) ofthe type illustrated in FIGS. 3A and 3B is inserted into the circularaperture defined by the ciliary sulcus (6) in place of the zonularligament (7) and the natural lens (4). The posterior spiral haptics ofthe posterior lens hold the posterior lens in place against the ciliarysulcus. As a result, the central axis of the anterior lens is axiallyoffset from the central axis of the posterior lens. Light rays (50)entering the eye parallel to the central axis of the anterior lens passtherethrough to the posterior lens to be refracted by (51) it to a focalpoint on the macular offset from the fovea and of un-degeneratedcondition.

FIG. 6 schematically shows the same arrangement as shown in FIG. 5except that the posterior lens is a posterior lens of the typeillustrated in FIGS. 4A and 4B.

In the arrangements illustrated in FIGS. 5 and 6, the optical trainprovided by the anterior and posterior lenses is such that the centralaxes of the two lenses are substantially parallel, though axiallyoffset.

FIG. 7 schematically illustrates the relationship between anteriorconverging (20) and posterior diverging (30) lenses in the lens train ofpreferred embodiments of the invention (haptics not shown). Thedimensions of the lenses are exaggerated. An axial offset (Δ) results inthe axial offsetting of the focal point of the lens train as illustratedin FIG. 8. The anterior converging lens (L1) has a positive power (e.g.+53 dioptres) and a focal point (F1) located upon the central axis (O1)of the lens. The anterior lens may be 5 mm in diameter. Symmetricalhaptics (not shown) may extend to a maximal distance from opposite edgesof the lens of 4 mm therefrom each (e.g. the anterior converging lensunit may be 13 mm across at its widest point). The posterior diverginglens (L2) has a negative optical power (e.g. −64 dioptres) and a focalpoint (F2) located upon its central axis (O2). The posterior lens may be7 mm in diameter and may have a lesser haptic (not shown) extending fromthe edge of the posterior lens to a maximal distance of 2 mm therefrom,and a greater haptic (not shown) extending from the opposite edge of theposterior lens to a maximal distance of 4 mm thereform (e.g. theposterior diverging lens unit may be 13 mm across at its widest point).

The central axis (O2) of the posterior lens is parallel to the centralaxis (O1) of the anterior lens and axially offset therefrom by adisplacement Δ (e.g. between 0.5 and 2 mm, such as 1 mm). The posteriorlens is located between the anterior lens and the focal point (F1) ofthe anterior lens. The anterior lens is located between the posteriorlens and the focal point (F2) of the posterior lens. Light rays incidentupon the anterior lens parallel to its central axis are focussed by thelens train at a focal point (F3) offset from the central axis (O1) ofthe anterior lens rays in a direction opposite to the axial offset (A)of the central axis (O2) of the posterior lens.

Since, in the so-called “thin lens approximation”, an axially parallellight ray incident upon the anterior lens surface (L1) at its lens partof maximum lens thickness must pass through the lens un-refracted, andmust then be refracted by the posterior lens (L2) in a direction whichmust trace back to the focal point (F2) of the posterior lens, theangular deviation (θ) of the focal point (F3) of the lens train from thecentral axis (O1) of the anterior lens is given by:

Θ=arctan(Δ/f ₂)

where f₂ is the focal length of the posterior diverging lens (L2). Ofcourse, thick lenses may be employed which may not entirely conform tothis relation, and the approximation of thin lenses upon which it isbased, but in general the deviation of the focal point (F3) of the lenstrain is in proportion to, and oppositely directed to, the axial offsetof the lenses. The angular deviation (Θ) may be about 15 degrees.

FIGS. 9 and 10 illustrate schematically the lens train of FIGS. 7 and 8with different haptic and posterior lens designs to achieve axialoffset.

Thus, a lens train may be provided for forming an image of an object orscene at an un-degenerated part of the macula.

A first substantially circular aperture is provided by the periphery ofthe ciliary sulcus and in parallel opposition to that a secondsubstantially circular aperture is provided by the eye wall parts wherethe iris meets the eye wall. The centres of the first and secondapertures are in register naturally. First the diverging posterior lensunit may be mounted within the first aperture, such that haptics thereofabut opposite first aperture edges. The posterior lens berotated/revolved within the first aperture to revolve the lens part ofminimal lens thickness about the centre of the first aperture. Thisrevolves the focal point (3) of the lens train ultimately provided whenthe anterior lens is put in place. Accordingly, a selection of thelocation, on the retina, of images formable by the lens train in use maybe made until an optimal part of the retina is found.

Completion of the lens train is then done by mounting the converginganterior lens within the second aperture such that haptics thereof abutopposite second aperture edges. The lens train may provide amagnification factor of between 1.0 and 1.5 (e.g. 1.2 to 1.4).

The posterior lens unit, and optionally the anterior lens unit may bemade of hard hydrophilic acrylic material such as polymethylmethacrylate (PMMA) etc, or soft hydrophilic or hydrophobic acrylicmaterial including but not limited to polymers containing hydroxyethylmethacrylate (HEMA), silicon hydrogel, etc.

Accordingly, the posterior lens, and/or the anterior lens, may berolled-up before being inserted into the eye through a small incision,thereafter to be unfurled and positioned within the eye as required.

Manufacturing the posterior intraocular lens such as is described above,may comprise: providing a lens template; lathing inner surface parts ofopposite sides of the lens template to define circular, concave oppositesurface regions providing a lens between which is defined a lens part ofminimal lens thickness corresponding to the central axis of the lens (onwhich the focal point of the lens resides); milling away outer parts ofthe lens template around and up to the edge of the concave inner lenssurface parts to form the outer periphery of the diverging lens and thehaptics which extend from it. The lens central axis may correspond tothe middle of the lathed concave surfaces when the milling does notremove any such lathed parts. FIGS. 3A and 3B is an example.

The method may include forming the outer lens periphery by milling awaylathed portions of the concave inner lens surface to form the diverginglens and the haptic(s) extending from its edges. The remaining concavelens may then have a circular periphery enclosing the central axisoffset from the middle of the lathed concave surfaces remaining. FIGS.4A and 4B is an example.

The examples described herein are intended as non-limiting andvariations and modification such as would be readily apparent to theskilled person are encompassed by the scope of the invention such as isdefined by the claims.

1-22. (canceled)
 23. A posterior intraocular lens apparatus including:diverging lens shaped to define as between opposite operative lenssurfaces a lens part of minimal lens thickness surrounded by lens partsof greater lens thickness; a haptic extending from the diverging lens toa first haptic part at an intermediate distance from the lens part ofminimal lens thickness, and further extending from the diverging lens toa second haptic part at a maximal distance from the lens part of minimallens thickness; wherein the maximal distance is greater than theintermediate distance and the second haptic part opposes the firsthaptic part across the lens part of minimal lens thickness.
 24. Aposterior intraocular lens apparatus according to claim 23 in which thehaptic comprises an arcuate limb incorporating the first and secondhaptic parts.
 25. A posterior intraocular lens apparatus including:diverging lens shaped to define as between opposite operative lenssurfaces a lens part of minimal lens thickness surrounded by lens partsof greater lens thickness; a first haptic extending from the diverginglens to a first haptic part at a first maximal distance from the lenspart of minimal lens thickness; a second haptic separate from the firsthaptic and extending from the diverging lens to a second haptic part ata second maximal distance from the lens part of minimal lens thickness;wherein the second maximal distance is greater than the first maximaldistance.
 26. A posterior intraocular lens apparatus according to claim25 in which the first haptic part opposes the second haptic part acrossthe lens part of minimal lens thickness.
 27. A posterior intraocularlens apparatus according to claim 23 or claim 25 in which the one oreach of the first and second haptics respectively comprises an arcuatelimb.
 28. A posterior intraocular lens apparatus according to claim 23or claim 25 in which the lens part of minimal lens thickness issubstantially in the middle of the operative lens surface(s).
 29. Aposterior intraocular lens apparatus according to claim 23 or claim 25in which the lens part of minimal lens thickness is offset from themiddle of the operative lens surface(s) towards a periphery thereof. 30.A posterior intraocular lens apparatus according to claim 23 or claim 25in which a plane containing first and second haptic parts contains thelens part of minimal lens thickness.
 31. A posterior intraocular lensapparatus according to claim 23 or claim 25 in which the periphery ofthe diverging lens presents a sighting lug indicating the peripheralpart of the diverging lens located between the second haptic part andthe lens part of minimal lens thickness.
 32. A posterior intraocularlens apparatus according to claim 23 or claim 25 in which the first andsecond haptic parts are peripheral parts of the apparatus.
 33. Aposterior intraocular lens apparatus according to claim 23 or claim 25in which the diverging lens comprises a plano-concave lens.
 34. Aposterior intraocular lens apparatus according to claim 23 or claim 25in which the diverging lens comprises a concavo-concave lens.
 35. Aposterior intraocular lens apparatus according to claim 23 or claim 25wherein in which the diverging lens is flexible.
 36. An intraocular lensapparatus including the posterior intraocular lens according to claim 23or claim 25 and further comprising a converging lens adapted tocooperate with the diverging lens as an anterior intraocular lens. 37.An intraocular lens apparatus according to claim 36 in which theconverging lens includes one or more haptics which extend away from theconverging lens in a direction partially transverse to the planecontaining the circumference of the lens to one common side of thatplane.
 38. An intraocular lens apparatus according to claim 36 in whichthe converging lens is shaped to define as between opposite operativelens surfaces a lens part of maximal lens thickness surrounded by lensparts of lesser lens thickness and includes a third haptic extendingfrom the converging lens to a third haptic part at a third maximaldistance from the lens part of maximal lens thickness, and a fourthhaptic separate from the third haptic and extending from the converginglens to a fourth haptic part at a fourth maximal distance from the lenspart of maximal lens thickness.
 39. A method of providing a lens trainfor forming an image of an object or scene including: providing anintraocular lens apparatus according to claim 36; placing the converginglens between the diverging lens and the object or scene to be imagedsuch that an operative lens surface of the converging lens opposes anoperative lens surface of the diverging lens and such that the lens partof minimal lens thickness does not oppose the lens part of maximalthickness.
 40. A method of providing a lens train according to claim 39including: providing a first substantially circular aperture in parallelopposition to a second substantially circular aperture such that thecentres of the first and second apertures are in register; mounting thediverging lens within the first aperture such that haptics thereof abutopposing first aperture edges; mounting the converging lens within thesecond aperture such that haptics thereof abut opposing second apertureedges.
 41. A method according to claim 40 including rotating the mounteddiverging lens within the first aperture thereby to revolve the lenspart of minimal lens thickness about the centre of the first aperturethereby to select the location of images formable by the lens train inuse.
 42. A method of manufacturing a posterior intraocular lensaccording to claims 23 or claim 25 including: providing a lens template;shaping inner surface parts of the lens template to define oppositesurfaces of a lens between which is defined a lens part of minimal lensthickness surrounded by lens parts of greater lens thickness; shapingouter surface parts of the lens template around said inner surface partsto form said diverging lens and said haptic(s).
 43. A method ofmanufacturing a posterior intraocular lens according to claim 42including shaping portions of said inner surface parts defining saidlens to form said diverging lens and said haptic(s).
 44. A method ofmanufacturing a posterior intraocular lens according to claim 43including shaping said inner surface parts to form a symmetricalconcavity with a circular periphery centred upon the lens part ofminimal lens thickness and forming therefrom the diverging lens with alens periphery centred upon other than the lens part of minimal lensthickness.